This invention relates to burners for gas turbine power plants and particularly to the construction thereof including means for eliminating the lip of conventional louver type burners without impairing its cooling capabilities.
As is well known in combustor technology the lip of the louver in a burner is its most vulnerable portion necessitating the highest percentage of maintenance relative to the entire combustor. Conventionally, the burner is fabricated from sheet metal joined to form a louver configuration with an extending lip. In recent years some effort has been employed to fabricate the burners by machining stock material into the burner configuration. Exemplary of a machined louvered burner is U.S. Pat. No. 3,373,152 granted to J. D. Wilson on June 5, 1973. The louvered construction of the burner described in the above-mentioned patent shows a conical intermediate portion having a plurality of drilled holes that have a prescribed dimension. The purpose of the drilled holes is to coalesce the airstream to form a film over the hot surfaces for cooling the same.
A disadvantage of the circular hole construction of the above-mentioned patent is that it has a consequential limitation on the amount of cooling air that can be employed. This patent, supra, does not recognize that both the cooling and structural aspects can be considered in order to control the temperature gradients so as to minimize thermally induced stresses.
In another area of differences, and in accordance with the teachings of this invention, the array of holes and slots are judiciously selected to not only provide the necessary film of cooling air to cool the burner liner but to also control the temperature across the elbow portion of the liner and provide hole configuration to prevent hot gas recirculation which would otherwise reduce the effectiveness of the cooling film.
Also, in accordance with the teachings of this invention, the wall thickness of the liner is varied so as to minimize stress concentrations and minimize louver stresses and this aspect is combined with judiciously sized and located cooling holes to control the temperature gradient so as to minimize thermally induced stresses.